# ASIN

 Syntax ASIN (x) Location QL ROM

This function calculates the arc-sine (in radians) which is the opposite of the sine function, ie:

x = SIN ( ASIN ( x )) = ASIN ( SIN ( x ))

The only valid values of x are in the range -1…1. This means that the range of angles supported by this command are -PI/2…PI/2. A negative angle means that the hypotenuse appears below the base line of the triangle (you must therefore always bear the orientation of the screen in mind when using this command).

Example

Given that there are two points on the screen at (10,20) and (100,75), find the angle of the line between those two points (from the horizontal):

```100 PRINT CALC_ANGLE(10,20 TO 100,75)
110 STOP
120 :
200 DEFine FuNction CALC_ANGLE(x1,y1,x2,y2)
220  Distan = SQRT((x2-x1)^2 + (y2-y1)^2)
230  Radian_angle = ASIN((y2-y1) / Distan)
250 END DEFine
```

MINERVA NOTE

On a Minerva you can replace line 220 with: 220 Distan = ABS(x2-x1,y2-y1)

CROSS-REFERENCE

ACOS, ATAN, ACOT are other arc functions, SIN, COS, TAN and COTtheir relatives.

Please also see the Mathematics section of the Appendix.

Compare ARSINH.